I am coming from Unity and I am looking into possibly diving in with this engine. My first big question I have is what would be the basic steps needed to create my own custom editor. Say for example I wanted to port over my item creation tool from Unity. Creating an editor script in unity just required me to inherit from UnityEditor.Editor and then initialize the window. Is the workflow similar here?
Unfortunately the APIs/ability to create custom editors for Game Studio have not been made available yet. An item is on their trello board for such features. See Plugin system